A burner tile, functioning as a refractory member, surrounds a burner attached to a roof or a side wall of, for example, a reheating furnace or a heat treatment furnace. Examples of widely used burner tiles include a rammed and molded product made of a plastic refractory material and a casted and molded product made of a castable material. For the rammed and molded product made of a plastic refractory material, high skill is required in molding. In some cases, the casted and molded product made of a castable material may explode due to insufficient drying. Furthermore, the burner tile suffers from severe thermal shock caused by heavy switching between burning and extinguishing operations of the burner. Disadvantageously, the burner tile tends to crack or peel off.
In recent years, the use of burner tiles made of ceramic fiber resistant to thermal shock has been being increased.
Patent Literature 1 discloses a ceramic fiber burner tile constructed such that ceramic fiber blankets are laminated in a cross, radial, or mosaic pattern and ends of fibers of the ceramic fiber blankets face a divergent or cylindrical burner attachment hole that extends axially through the burner tile and increases in diameter toward a furnace interior.
Patent Literature 2 discloses a burner tile including a refractory material and an inorganic fiber cloth such that the inorganic fiber cloth is rolled.
Patent Literature 3 discloses a molded inorganic fiber product fabricated by impregnating a needled inorganic fiber blanket with an inorganic sol and drying the blanket. The molded inorganic fiber product has a bulk density of 0.08 to 0.20 g/cm3. Patent Literature 3 describes the use of this product as a heat insulator for a burner tile, for example.
Patent Literature 4 discloses a molded inorganic fiber product that includes inorganic fiber and inorganic binder particles and has at least one combination of a high fiber density region and a low fiber density region. The ratio of the binder particle content in the high fiber density region to that in the low fiber density region is 0.5:1 to 5:1. The number-average particle diameter of the inorganic binder particles is 20 to 35 μm and the number of inorganic binder particles is less than 15 in the outermost surface of the molded product.
Patent Literature 5 discloses a burner tile that includes an enclosure made of a heat-resistant material, a molded inorganic fiber blanket compressed in a cavity in the enclosure, and a liner member retained by restoring force of the molded inorganic fiber blanket.
Patent Literature 6 discloses a burner tile that includes a plurality of ceramic fiber blankets laminated, a combustion cylindrical hole extending perpendicular to a laminating direction of the blankets and having a divergent longitudinal sectional shape such that the cylindrical hole increases in diameter toward one end thereof, and molded fiber products arranged on both sides of the burner tile in the laminating direction. The molded fiber products are made by compressing and combining ceramic fiber with a binder.
Patent Literature 7 discloses a burner tile that includes continuous layers of inorganic fiber blankets forming an inner circumferential surface to be in contact with a furnace core. The continuous layers are next to one another in a plane perpendicular to the axis of a main hole for a burner, and increase in their bulk density toward the axis.
Patent Literature 1: Japanese Patent Publication H6-281132A
Patent Literature 2: Japanese Patent Publication H9-264528A
Patent Literature 3: Japanese Patent Publication 2011-208344A
Patent Literature 4: International Publication WO 2013/035645
Patent Literature 5: Japanese Patent Publication 2000-9305A
Patent Literature 6: Japanese Patent Publication H7-69051B
Patent Literature 7: Japanese Patent Publication S61-59113A
To ensure contact and mixing of a fuel emitted from a burner with combustion air under high velocity conditions and achieve high temperature combustion, burner tiles are required to have high fire resistance, high heat resistance, high erosion resistance, high thermal shock resistance, and uniform thermal conductivity.
The burner the disclosed in Patent Literature 1 includes ceramic fiber. Velocities exceeding approximately 35 m/s increase the amount of fibers scattering. This burner the can hardly withstand high velocities above 100 m/s. It is difficult to ensure sufficient stirring in a furnace with a flame emitted from a burner at a high velocity.
The burner tile disclosed in Patent Literature 2 is heavy and exhibits poor handling because its material matrix is a castable material, and further requires preheating to prevent cracks. Since this burner tile is produced by cast molding, spare parts cannot be provided. Disadvantageously, the burner tile still has disadvantages in that the burner tile requires a long period for reconstruction and replacement when broken.
Furthermore, this burner tile includes only one blanket having a single needling density, and thus has disadvantages in terms of moldability and properties. Specifically, a high-needling-density blanket having high resilience may create difficulty in achieving highly accurate molding for making a product having a shape that may result in large strain, for example, a block-shaped product. A low-needling-density blanket may degrade the properties, such as erosion resistance, of the burner tile.
The burner tile disclosed in Patent Literature 3 has disadvantages in that delamination tends to occur when a laminated structure is formed.
In the burner tile disclosed in Patent Literature 4, the number of inorganic binder particles in the outermost surface of the molded product is small, less than 15. Disadvantageously, it is difficult to maintain the outside shape of a final product produced by molding a needled blanket having high resilience into a block shape.
In the burner tile disclosed in Patent Literature 5, the liner member, which includes heat resistant long fiber, heat resistant powder, and aluminum phosphate, is thin. Disadvantageously, the heat resistance cannot be maintained for a long term.
The burner tile disclosed in Patent Literature 6 includes the simple laminate of ceramic fiber blankets bonded with a silica sol. Shrinkage of the ceramic fiber blankets may form a clearance between the ceramic fiber blankets, and the clearance may serve as a heat bridge.
In the burner tile disclosed in Patent Literature 7, the superposed surfaces of ceramic fiber blankets laminated radially in an orifice tube may serve as heat bridges.